1. Field of the Invention
The present invention relates to a three-dimensional processor for processing three-dimensional data obtained by measurement with a three-dimensional measurement device using, for example, a light projection method, a method for controlling display of the three-dimensional data in the three-dimensional processor, and a computer program product.
2. Description of the Related Art
A three-dimensional measurement device using a light section method, which is a kind of the light projection method, obtains raw measurement data by projecting slit light, as measurement light, onto an object to be measured, optically scanning the object with the slit light, and receiving the measurement light reflected from the object (reflected light) with an image sensor. The raw measurement data thus obtained are used to perform an operation for three-dimensional processing based on the principle of triangulation, so that three-dimensional data (also called three-dimensional coordinate data, coordinate data, or distance data) indicating three-dimensional position coordinates of each point on the surface of the object are obtained (Japanese Laid-open Patent Publication No. 9-325009).
Three-dimensional data obtained by a three-dimensional measurement device are data indicating three-dimensional position coordinates of a plurality of points on the surface of an object to be measured, or a set of such data. A plurality of pieces of three-dimensional data obtained by performing measurement on different parts of the object is combined with one another; thereby, three-dimensional shape data (a three-dimensional model) of the entire surface of the object can be obtained. Alternatively, raw measurement data obtained by a three-dimensional measurement device may be transferred to a computer and the computer performs an operation for three-dimensional processing. Note that the light projection method in which spot light, step light, or density pattern light is projected instead of slit light is also known.
In the case where a three-dimensional measurement device is used to perform measurement on an object to be measured and the intensity of a signal of reflected light from the object is substantially high or substantially low, accurate data may not be obtained. For example, when the signal intensity is substantially high, the output of an image sensor is saturated and, therefore, the correct light-receiving position cannot be specified. As a result, accurate data cannot be obtained. The signal intensity is substantially high in the case where specular reflection or reflection similar thereto occurs on the surface of the object. On the other hand, when the signal intensity is substantially low, the S/N ratio deteriorates due to noise. As a result, accurate data cannot be obtained. The signal intensity is substantially low, for example, in the case where the object is distant from the three-dimensional measurement device or the normal direction of the surface of a part of the object is not toward the three-dimensional measurement device and the angle of incidence of measurement light is substantially large.
In order to deal with the cases where the signal intensity is substantially high or substantially low, the following procedure has been performed in conventional systems. A threshold is set to a signal level. Data indicating a signal intensity that does not fall within an ideal range are discarded, and only highly reliable data indicating a signal intensity that falls within the ideal range are outputted (Japanese Laid-open Patent Publication No. 2006-23178).
A device described in Japanese Laid-open Patent Publication No. 2006-23178 is configured to determine a phase value having reliability for each pixel of two-dimensional data. The device is not, however, configured to enable a user to select the reliability.
When a three-dimensional measurement device is used to perform measurement, the intensity of a signal obtained by the measurement changes considerably depending on, for example, gloss, a color, a shape of the surface of an object to be measured. It is, therefore, difficult to set a threshold level suitable for all the conditions. As a result, in some cases, data having no reliability are outputted or necessary data are not outputted.